Southern pig-tailed macaques are buff-brown in colour, with a darker back and crown. Their eyes are a light amber. A red streak of hair extends from the corner of each eye, appearing almost like eyeliner. ​Males have mane-like hair framing their faces that the females lack. Males also have larger canine teeth, usually almost twice as long as females’. Their face and belly are a light cream colour, and they often have a yellowish tinge. They have short, hairless or nearly hairless tails that they carry half-erect, giving them a pig-like appearance, hence their name. Infants are born with a solid black coat but begin to develop their adult colouring when they are about three months of age.